May Global Warming: Recent Developments and the Outlook for the Pacific Northwest

Transcription

1 Global Warming: Recent Developments and the Outlook for the Pacific Northwest Pat Bartlein Department of Geography University of Oregon Global Warming: Recent Developments and the Outlook for the Pacific Northwest A short review of recent environmental change instrumental record other indicators of global warming Issues and debates about observed warming the satellite record the hockey-stick curve do climate models really work? The greenhouse effect and the IPCC projections Model testing using the paleoclimatic record (why we should believe the models) What s next? projected changes in vegetation projected changes in hydrology May Vanity Fair (May, 2006) 1

2 Global temperature change since 1880 Global temperature change since was warmest year since 1880 NOAA: was second warmest year since 1860 CRU: Climate Anomalies NASA GISS The highest global surface temperature in more than a century of instrumental data was recorded in the 2005 calendar year in the GISS annual analysis. However, the error bar on the data implies that 2005 is practically in a dead heat with 1998, the warmest previous year. It s always warmer, colder, wetter, or drier than normal somewhere Summer 2005 NCDC National Climatic Data Center NCDC National Climatic Data Center 2

3 August 2005 Summer 2005 Warmest on record in N. Hemisphere NCDC National Climatic Data Center The past 100 years -- global precipitation trend N. Hemisphere Sea-Ice warmer atmosphere = wetter atmosphere Climatic Research Unit (CRU UEA) (December, 2005) Mtn. glacier trends Observed sea-level trends Dyurgerov and Meier (2000) IPCC WG1 TAR (2001) IPCC WG1 TAR 3

4 Ocean heat content changes Western U.S. Winter Snowpack Impacts decrease increase Trends in Apr 1 Snow-water equivalent source: Levitus et al. (2000) Mote, et al. (2005, Bulletin AMS) Timing of snowmelt runoff Trends in snowmelt timing Stewart et al. (2004, Climatic Change) Stewart et al. (2004, Climatic Change) Recent global and hemispheric average temperature trends Recent temperature anomalies: it s warm, but is that warmth unprecedented? IPCC, Climate Change 2001 Recent global and hemispheric average temperature trends Three major issues: satellites vs. surface obs. who s right? Mann et al. methodology how robust? climate models, do they really work? IPCC, Climate Change

5 Variations among global temperature analyses Satellite and surface temperature reconciliation Vose et al. (2005, GRL) Formerly small warming trend gets larger U.S. Climate Change Science Program Mears et al. (2005, Science) Kerr (2006, Science) What about the hockey stick? 20 th Century is still warmest Science (2005) Nature (2005) 5

6 Mountain glacier retreat & inferred temperature Do climate models work? Science (2004, 2005) Oerlemans (2005, Science) An Ideal World A more realistic world E A B C D A B C D A more realistic world E Even more realistic I H E G E2 A B C D F A B C D F 6

7 Amplification of CO 2 effects? river runoff ocean thermohaline circulation?? atmospheric CO 2 atmospheric water vapor longwave radiation absorbtion additional warming (feedback) carbon release from terrestrial biosphere snow and ice clouds total anthropogenic warming Amplification of CO 2 effects? river runoff ocean thermohaline circulation?? atmospheric CO 2 atmospheric water vapor longwave radiation absorbtion additional warming (feedback) carbon release from terrestrial biosphere snow and ice clouds total anthropogenic warming Earth-atmosphere energy balance The Intergovernmental Panel on Climate Change (IPCC) greenhouse effect IPCC WG1 TAR Climate Change 2001 CO 2 increase Temporal and spatial variations of CO 2 Pre-Industrial = 280 ppm NOAA NOAA 7

8 Greenhouse gas emissions World Resources Institute Climate Analysis Indicators Tool (CAIT) Increasing CO 2 comes from fossil fuel NOAA World Resources Institute World Resources Institute Per-capita emissions Radiative forcing histories 3.0 IPCC GHG note: different scales Solar Aerosols Volcanos

9 Impacts of emissions on climate -- radiative forcing IPCC Emissions scenarios (2000) IPCC WG1, Climate Change 2001, The Scientific Basis IPCC Third Assessment Projections (2001) General Circulation Models (GCMs) & The Primitive Equations source: Hadley Centre IPCC WG1 TAR Climate Change 2001 Temperature change ( SRES A2) Temperature change ( SRES B2) source: IPCC WG1 TAR Climate Change 2001 source: IPCC WG1 TAR Climate Change

10 Precipitation change ( SRES A2) Precipitation change ( SRES B2) source: IPCC WG1 TAR Climate Change 2001 source: IPCC WG1 TAR Climate Change 2001 Why should we believe the climate models? Climate models (GCMs) have long been used in numerical weather prediction Geologic record shows importance of GHGs on climate high GHGs = warm; low GHGs = cold Greenhouse gases play an important role in amplifying the orbital pacemaker Paleoclimatic data-model comparisons Last Glacial Maximum (21,000 years ago) to present natural experiment : models explain past climatic variations pretty well Other data-model comparisons Carbon dioxide and Phanerozoic Climate Change CO 2 Glaciation Royer et al. (2004, GSA Today) Insolation and ice-volume variations Orbital variations are pacemaker of ice ages Orbital variations pacemaker of the Ice Ages 10

11 Vostok Ice Core record: GHGs and temperature Paleoclimatic data-model comparisons Nature does experiments with real climate system Environmental change research provides evidence of the outcome of the experiment and what the controls were Replicate Nature s experiment using a climate model Compare the climate-model output with syntheses of paleoenvironmental data (pollen data, lake-status data) Mismatches are great: they tell us what concepts or ideans are not completely understood (and where that happens) Petit et al. (1999, Nature) Retreat of the Laurentide Ice Sheet Insolation North and South Carp Lake, WA: Fossil-pollen record Vegetation tracks climate change 11

12 Circulation-produced regional contrasts Jet south Jet north STH & Monsoon LGM circulation, temperature and the glacial world 21,000 years ago Today Dry Wet Dry Dry Wet Wet Wet Wet 21,000 14,000 11, (years ago) Thompson, Whitlock, Bartlein, Harrison, and Spaulding (1993, in Global Climates since the Last Glacial Maximum) Atmospheric circulation around North America Pacific Northwest climate controls 6000 years ago Simulations over past two millennia The outlook for the Pacific Northwest Potential hydrologic changes continuation of trends toward earlier snowmelt, reduced SWE more winter precipitation (as rain instead of snow)? less summer precipitation? Potential vegetation changes more forest/less steppe different communities Jones and Mann (2004, Rev. Geophys. 12

13 Projected changes in snowmelt timing IPCC Fourth Assessment Stewart et al. (2004, Climatic Change) CA Streamflow Projections Present vegetation Sarah Shafer U.S. Geol. Survey Corvallis Dettinger et al. (2004, Climatic Change) Potential future vegetation Looking west across the Cascades Sarah Shafer U.S. Geol. Survey Corvallis Increased CO2 + warmer, wetter climate happier trees Sarah Shafer U.S. Geol. Survey Corvallis 13

14 Potential for change nearly everywhere The outlook for the Pacific Northwest Potential hydrologic changes continuation of trends toward earlier snowmelt, reduced SWE more winter precipitation (as rain instead of snow)? less summer precipitation? Potential vegetation changes more forest/less steppe different communities Things will be different different-looking landscape different availability of natural resources new climates Sarah Shafer, U.S. Geol. Survey, Corvallis.pdf file of slides 14